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using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
namespace Xamarin.Forms
{
public partial class VisualElement
{
sealed class MergedStyle : IStyle
{
////If the base type is one of these, stop registering dynamic resources further
////The last one (typeof(Element)) is a safety guard as we might be creating VisualElement directly in internal code
static readonly IList<Type> s_stopAtTypes = new List<Type> { typeof(View), typeof(Layout<>), typeof(VisualElement), typeof(Element) };
readonly BindableProperty _classStyleProperty = BindableProperty.Create("ClassStyle", typeof(IList<Style>), typeof(VisualElement), default(IList<Style>),
propertyChanged: (bindable, oldvalue, newvalue) => ((VisualElement)bindable)._mergedStyle.OnClassStyleChanged());
readonly List<BindableProperty> _implicitStyles = new List<BindableProperty>();
IStyle _classStyle;
IStyle _implicitStyle;
IStyle _style;
string _styleClass;
public MergedStyle(Type targetType, BindableObject target)
{
Target = target;
TargetType = targetType;
RegisterImplicitStyles();
Apply(Target);
}
public IStyle Style
{
get { return _style; }
set { SetStyle(ImplicitStyle, ClassStyle, value); }
}
public string StyleClass
{
get { return _styleClass; }
set
{
string val = string.IsNullOrWhiteSpace(value) ? null : value.Trim();
if (_styleClass == val)
return;
if (_styleClass != null)
Target.RemoveDynamicResource(_classStyleProperty);
_styleClass = val;
if (_styleClass != null)
Target.SetDynamicResource(_classStyleProperty, Forms.Style.StyleClassPrefix + _styleClass);
}
}
public BindableObject Target { get; }
IStyle ClassStyle
{
get { return _classStyle; }
set { SetStyle(ImplicitStyle, value, Style); }
}
IStyle ImplicitStyle
{
get { return _implicitStyle; }
set { SetStyle(value, ClassStyle, Style); }
}
public void Apply(BindableObject bindable)
{
ImplicitStyle?.Apply(bindable);
ClassStyle?.Apply(bindable);
Style?.Apply(bindable);
}
public Type TargetType { get; }
public void UnApply(BindableObject bindable)
{
Style?.UnApply(bindable);
ClassStyle?.UnApply(bindable);
ImplicitStyle?.UnApply(bindable);
}
void OnClassStyleChanged()
{
var classStyles = Target.GetValue(_classStyleProperty) as IList<Style>;
if (classStyles == null)
ClassStyle = null;
else
{
ClassStyle = classStyles.FirstOrDefault(s => s.CanBeAppliedTo(TargetType));
}
}
void OnImplicitStyleChanged()
{
var first = true;
foreach (BindableProperty implicitStyleProperty in _implicitStyles)
{
var implicitStyle = (Style)Target.GetValue(implicitStyleProperty);
if (implicitStyle != null)
{
if (first || implicitStyle.ApplyToDerivedTypes)
{
ImplicitStyle = implicitStyle;
return;
}
}
first = false;
}
}
void RegisterImplicitStyles()
{
Type type = TargetType;
while (true)
{
BindableProperty implicitStyleProperty = BindableProperty.Create("ImplicitStyle", typeof(Style), typeof(VisualElement), default(Style),
propertyChanged: (bindable, oldvalue, newvalue) => ((VisualElement)bindable)._mergedStyle.OnImplicitStyleChanged());
Target.SetDynamicResource(implicitStyleProperty, type.FullName);
_implicitStyles.Add(implicitStyleProperty);
type = type.GetTypeInfo().BaseType;
if (s_stopAtTypes.Contains(type))
return;
}
}
void SetStyle(IStyle implicitStyle, IStyle classStyle, IStyle style)
{
bool shouldReApplyStyle = implicitStyle != ImplicitStyle || classStyle != ClassStyle || Style != style;
bool shouldReApplyClassStyle = implicitStyle != ImplicitStyle || classStyle != ClassStyle;
bool shouldReApplyImplicitStyle = implicitStyle != ImplicitStyle && (Style as Style == null || ((Style)Style).CanCascade);
if (shouldReApplyStyle)
Style?.UnApply(Target);
if (shouldReApplyClassStyle)
ClassStyle?.UnApply(Target);
if (shouldReApplyImplicitStyle)
ImplicitStyle?.UnApply(Target);
_implicitStyle = implicitStyle;
_classStyle = classStyle;
_style = style;
if (shouldReApplyImplicitStyle)
ImplicitStyle?.Apply(Target);
if (shouldReApplyClassStyle)
ClassStyle?.Apply(Target);
if (shouldReApplyStyle)
Style?.Apply(Target);
}
}
}
}
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